Gowan Stevens' Grandfather

We know Gowan Stevens had a grandfather, because in The Town Charles Mallison mentions that Gowan's grandfather was his own grandfather's brother, but that doesn't tell us if Faulkner - or Temple Drake - actually has this man in mind when in Requiem for a Nun she tries to cover up what she was actually saying by telling Gowan that "I was telling Uncle Gavin he had something of Virginia or some sort of gentleman in him too that he must have inherited from you through your grandfather" (51-52). These are the only two mentions of this grandfather in the fictions.